KR102543990B1 - Method and apparatus for compensating scatter of X-ray image - Google Patents

Abstract

A scattering correction method for an X-ray image according to the present invention includes the steps of (a) receiving an original X-ray image; (b) initializing a primary image with the original X-ray image; (c) estimating a scattering image from the primary image; (d) updating the primary image using the original X-ray image and the scattering image; (e) determining whether an end condition is satisfied; (f) if the termination condition is not satisfied, repeating steps (c) to (e) using the primary image updated through step (d) as the primary image for step (c); and (g) outputting the primary image updated through step (d) as a scattering-corrected image if the termination condition is satisfied.

Description

Method and apparatus for compensating scatter of X-ray image {Method and apparatus for compensating scatter of X-ray image}

The present invention relates to a scattering correction method and apparatus for an X-ray image, and more particularly, to a scattering correction method for an X-ray image capable of obtaining a scattering-corrected image from an original X-ray image without using a scattering removal grid, and It's about the device.

An X-ray imaging device is a device that obtains an image by using the property of an object and attenuation according to the distance while X-rays pass through an object. It is widely used in the field of non-destructive testing. Recently, in an X-ray imaging device, a digital method of acquiring an image using a digital X-ray detector has replaced the conventional film method.

On the other hand, when radiation passes through an object, phenomena such as the photoelectric effect and Compton scattering occur. Due to this phenomenon, the photons may go straight in the direction in which they are incident on the subject (primary beam), or the traveling direction may be changed (scattered beam). Images created by detecting primary and scattered rays by the detector are called primary images and scattered images, respectively.

The primary line expresses the image information correctly, but in the case of the scattering line, the energy loss increases as the scattering angle increases due to Compton scattering, which is the main scattering phenomenon, so the image information is spread based on the detection position. In the detector, an image obtained by overlapping a primary image by a primary ray and a scattering image by a scattering ray is obtained. The scattering image blurs the primary image and lowers the contrast of the image, resulting in deterioration of image quality.

Hitherto, a scattering removal grid has been used to remove scattering. The scattering ray removal grid is a device in which a material with a high radiation attenuation coefficient (absorption part) and a material with a low radiation attenuation (transmitting part) are alternately arranged. By arranging the transmission part according to the expected direction of movement of the first line determined by the imaging structure, the first line passes through. and block the scattering rays. An example of a scattering ray removal grid is disclosed in Korean Patent Registration No. 10-1320891.

Scattered rays can be removed through the scattering ray removal grid, but since the absorbing portion non-selectively removes not only the scattered rays but also the first-order rays, the amount of X-ray irradiation must be increased to compensate for the loss of signal-to-noise ratio. In addition, if the traveling direction of the first line according to the shooting structure is not accurately aligned with the transparent part, it may not be able to exert proper effects such as artifacts in the image, and thus the convenience of shooting work for accurate alignment is reduced. there is

Republic of Korea Patent Registration No. 10-1320891 (Announced on October 23, 2013)

An object of the present invention is to provide a scattering correction method and apparatus for an X-ray image capable of effectively removing scattering components from an X-ray image through image processing without using a scattering ray removal grid.

A scattering correction method for an X-ray image according to the present invention for solving the above technical problem includes: (a) receiving an original X-ray image; (b) initializing a primary image with the original X-ray image; (c) estimating a scattering image from the primary image; (d) updating the primary image using the original X-ray image and the scattering image; (e) determining whether an end condition is satisfied; (f) if the termination condition is not satisfied, repeating steps (c) to (e) using the primary image updated through step (d) as the primary image for step (c); and (g) outputting the primary image updated through step (d) as a scattering-corrected image if the termination condition is satisfied.

In the step (d), the primary image may be updated according to a difference or ratio between the original X-ray image and the sum image of the primary image and the scattering image based on the primary image.

In the step (c), the scattering image may be estimated using a scattering kernel defined for each thickness.

The step (c) may include generating a water equivalent thickness (WET) map from the flat field image and the primary image; and estimating the scattering image using the WET map and the scattering kernel.

In the generating of the WET map, a first WET map is generated from a flat field image and the primary image, and a value of a pixel corresponding to a direct irradiation region of the original X-ray image is set to 0. It can be converted into the WET map using a region of interest mask having .

The direct irradiation area of the original X-ray image may be an area in which a pixel value is greater than a predetermined threshold value.

In the generating of the WET map, a first WET map is generated from a flat field image and the primary image, and the first WET map corresponds to a field of view according to a collimator in the original X-ray image. It can be converted into the WET map using a visual field map having a probability value as a pixel value.

In the step (e), the end condition may be determined according to a difference or ratio between the primary video updated in the step (d) and the primary video in the step (c).

In the step (e), the end condition may be determined according to the number of repetitions of the steps (c) to (e).

An X-ray image scattering correction device according to the present invention for solving the above technical problem includes an image input unit for receiving an original X-ray image; and an image processing unit outputting a scattering-corrected image of the original X-ray image, wherein the image processing unit initializes a primary image with the original X-ray image and estimates a scattering image from the primary image. Process 1, a second process of updating the primary image using the original X-ray image and the scattering image, and a third process of determining whether an end condition is satisfied are performed, and if the end condition is not satisfied, the The first to third processes are repeatedly performed using the primary image updated through the second process as the primary picture for the first process, and if the end condition is satisfied, the primary updated through the second process It is characterized in that the head image is output as a scattering-corrected image.

The image processing unit may update the primary image according to a difference or ratio between the original X-ray image and the sum image of the primary image and the scattering image based on the primary image in the second process. there is.

In the first process, the image processor may estimate the scattering image using a scattering kernel defined for each thickness.

The image processing unit may generate a water equivalent thickness (WET) map from the flat field image and the primary image in the first process, and estimate the scattered image using the WET map and the scattering kernel.

The image processing unit generates a first WET map from the flat field image and the primary image in the first process, and converts the first WET map to a pixel value corresponding to a direct irradiation area of the original X-ray image. It can be converted to the WET map using a region of interest mask having 0.

The direct irradiation area of the original X-ray image may be an area in which a pixel value is greater than a predetermined threshold value.

The image processing unit generates a first WET map from the flat field image and the primary image in the first process, and converts the first WET map to a field of view according to a collimator in the original X-ray image. The WET map may be converted using a field of view map having a corresponding probability value as a pixel value.

The end condition may be determined according to a difference or ratio between the primary video updated through the second process and the primary video in the first process.

The termination condition may be determined according to the number of repetitions of the first to third processes.

According to the present invention, it is possible to effectively remove scattering components from an X-ray image through image processing without using a scattering ray removal grid.

1 is a block diagram of an X-ray image scatter correction device according to an embodiment of the present invention.
2 shows a flowchart of a method for correcting scattering of an X-ray image according to an embodiment of the present invention.
3 shows an example of a 3D visualization of a WET map.
4 shows an example of a flat field image.
5 is a one-dimensional graph of scattering kernels defined for various thicknesses.
6 shows an example of a scattering image estimated using a scattering kernel from a given X-ray image.
7 shows an example of a scattering corrected image obtained according to an embodiment of the present invention.
8 shows an example of a region-of-interest mask.
9 shows an example of a visual field map.
10 shows an enlarged portion of FIG. 9 .
11 shows an example of a WET map to which a region of interest mask and a field of view map are applied.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. Substantially the same elements in the following description and accompanying drawings are indicated by the same reference numerals, respectively, and redundant description will be omitted. In addition, in describing the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, a detailed description thereof will be omitted.

1 is a block diagram of an X-ray image scatter correction device according to an embodiment of the present invention. The X-ray image scatter correction device according to the present embodiment may include an image input unit 110 , an image processor 120 , and a database 130 .

The image input unit 110 receives an original X-ray image including scattering components. The image input unit 110 may receive an original X-ray image from the detector of the X-ray imaging device. X-ray imaging devices are of various types, such as general X-ray imaging devices for imaging the chest, arms, legs, etc., X-ray imaging devices using mammography, a mammography technique, and X-ray imaging devices using tomography. can be Depending on the embodiment, the original X-ray image is taken and stored in advance, and the image input unit 110 may receive the original X-ray image from an arbitrary storage medium or through a network.

The image processing unit 120 outputs a scattering-corrected image from the original X-ray image through image processing. To this end, the image processing unit 120 first initializes the primary image as an original X-ray image, estimates a scattering image from the primary image, and updates the primary image using the original X-ray image and the scattering image. By iterating, the finally updated primary image is output as a scattering-corrected image. The image processing unit 120 may output the scattering-corrected image to a display device (not shown). Depending on the embodiment, the image processing unit 120 may output the scattering-corrected image to an arbitrary storage medium or transmit the image to the outside through a network.

In the database 130, a flat field image and a scattering kernel are stored. The flat field image and the scattering kernel may be used in a process in which the image processing unit 120 estimates a scattering image from the primary image.

2 shows a flowchart of a method for correcting scattering of an X-ray image according to an embodiment of the present invention. Referring to FIG. 2 together, the X-ray image scattering correction device according to FIG. 1 will be described in more detail.

In step 210, the image input unit 110 receives an original X-ray image.

In step 220, the image processor 120 first initializes the primary image as an original X-ray image. As described above, the image processing unit 120 repeats the process of estimating the scattered image from the primary image and the process of updating the primary image. At first, since it does not have a primary image for estimating the scattered image, the scattered image For estimation, the primary image is initialized with the original X-ray image.

, 초기화된 프라이머리 영상을

, n번째 갱신된(즉, n번 반복에 따른) 프라이머리 영상을

로 나타내기로 한다. 여기서,

는 영상에서의 좌표를 나타낸다.Below, the original X-ray image

, the initialized primary image

, the n-th updated (i.e., according to n repetitions) primary image

to be represented by here,

represents coordinates in the image.

Initializing the primary image can be expressed by the following equation.

Steps 230 and 240 below correspond to a process in which the image processing unit 120 estimates a scattering image from the primary image.

In step 230, the image processing unit 120 generates a water equivalent thickness (WET) map from the flat field image and the primary image.

WET (water equivalent thickness) is the thickness when a subject is replaced with a water column, and the WET map is a map obtained by WET for each pixel of the image. FIG. 3 shows an example of a 3D visualization representation (right) of a WET map for a certain image (left).

에 대하여, WET 맵

은 Lambert-Beers law에 의해 다음 수학식을 이용해 근사적으로 구해질 수 있다.given primary video

Regarding, the WET map

can be approximated using the following equation by the Lambert-Beers law.

는 플랫 필드 영상으로, 원본 X선 영상과 동일한 촬영 조건(예컨대 관전압)에서 피사체 없이 촬영된 영상이다. 도 4는 플랫 필드 영상의 일 예를 보여준다. 플랫 필드 영상은 다양한 촬영 조건에 미리 촬영되어 촬영 조건 별로 예컨대 룩업 테이블(look-up table, LUT) 형태로 데이터베이스(130)에 저장될 수 있다. 실시예에 따라서, 플랫 필드 영상은 촬영 조건과 디텍터의 민감도를 이용하여 계산된 것이 사용될 수도 있다.

는 물의 선형 감쇄 계수(linear attenuation coefficient)인데, 관전압에 따라 정해지는 값이 사용될 수도 있고, 일반적인 촬영의 경우 특정 값(예컨대 0.2)이 사용될 수도 있다.here,

is a flat field image, and is an image captured without a subject under the same photographing conditions (eg, tube voltage) as the original X-ray image. 4 shows an example of a flat field image. Flat field images may be previously captured under various shooting conditions and stored in the database 130 in the form of, for example, a look-up table (LUT) for each shooting condition. Depending on the embodiment, a flat field image calculated using a photographing condition and a sensitivity of a detector may be used.

is a linear attenuation coefficient of water, a value determined according to the tube voltage may be used, or a specific value (eg, 0.2) may be used in the case of general imaging.

Referring back to FIG. 2 , in step 240, the image processing unit 120 estimates a scattered image from the primary image using a WET map and a scattering kernel.

가 주어질 때 산란 영상

는 Scatter Kernel Superposition (SKS)을 통해 추정될 수 있다. 이를 수학식으로 나타내면 다음과 같다.Generally, primary video

A scattering image given

can be estimated through Scatter Kernel Superposition (SKS). If this is expressed as a mathematical formula, it is as follows.

는

를 중심으로 입력된 펜슬 빔(pencil beam)의 임펄스 응답(또는, 이차원이므로 Point Spread Function(PSF)이라고도 함)으로서, 산란 커널(scatter kernel)로 칭해진다. 이처럼 산란 영상은 프라이머리 영상과 산란 커널의 컨벌루션(convolution) 연산으로 표현되며, 이를 Scatter Kernel Superposition (SKS)이라 한다. 디텍터에서 얻어지는 영상

는 다음 수학식과 같이 프라이머리 영상과 산란 영상의 단순 합으로 표현될 수 있다.Here, the integral area D is the irradiated area of the detector.

Is

As an impulse response (or, since it is two-dimensional, it is also referred to as a Point Spread Function (PSF)) of a pencil beam input centered on , it is called a scatter kernel. As such, the scattering image is expressed by a convolution operation between the primary image and the scattering kernel, and this is called Scatter Kernel Superposition (SKS). image obtained from the detector

Can be expressed as a simple sum of the primary image and the scattering image as shown in the following equation.

가 주어지면, 수학식 3, 4를 이용하여 프라이머리 영상

와 산란 영상

가 구해질 수 있다.Hence the scattering kernel

Given, the primary image using Equations 3 and 4

and the scattering image

can be saved

In general, assuming that the scattering kernel satisfies an isotropic property, the scattering kernel can be simply expressed as a scatter-primary ratio (SPR), which is a intensity according to a radius, without direction information. At this time, the thicker the object, the more scattering lines are generated. Therefore, a more similar result to the actual one can be obtained by defining the scattering kernel differently according to the thickness rather than using a fixed scattering kernel for a certain thickness. 5 is a one-dimensional graph of scattering kernels defined for various thicknesses.

In addition, since more scattering lines are generated as the tube voltage increases, the scattering kernel may be differently defined according to the tube voltage. Accordingly, scattering kernels for each tube voltage and each thickness may be stored in the database 130 in the form of a lookup table.

For example, the tube voltage may range from 60 kVp to 150 kVp in units of 1 kVp, and the thickness may range from 1 cm to 35 cm in units of 2 cm. A scattering kernel for a thickness of less than 1 cm may use a zero function to prevent scattering by a corresponding pixel. The scattering kernel stored in the database 130 may be created through various methods. For example, it can be measured through experiments by implementing an actual physical experimental environment, assumed as a mathematical function such as a Gaussian function, or obtained through Monte Carlo simulation such as EGSnrc, MCNP, and GATE by virtually implementing an experimental environment. Through these methods, the scattering kernel can be approximated as an isotropic two-dimensional low-pass filter.

Since the WET map is obtained through step 230, the scattering image can be estimated using the WET map and the scattering kernel defined for each thickness in step 240. Equation for estimating the scattering image can be expressed as follows.

는

로부터 추정되는 산란 영상을 나타내며,

는 i번째 두께 구간에 대해 정의된 산란 커널을 나타낸다.

는 i번째 두께 구간에 해당하는 픽셀들만을 추출하는 마스크로서, 다음 수학식과 같이 표현될 수 있다.here,

Is

Represents a scattering image estimated from

denotes the scattering kernel defined for the i-th thickness interval.

Is a mask for extracting only pixels corresponding to the i-th thickness section, and may be expressed as in the following equation.

는

에 대응하는 WET 맵을 나타내고,

은 i 번째 두께 구간을 나타낸다.here,

Is

Represents a WET map corresponding to

represents the ith thickness section.

6 shows an example of a scattering image (right) estimated using a scattering kernel from a given X-ray image (left).

In step 250, the image processor 120 updates the primary image using the original X-ray image and the scattering image. This process is for modifying the primary image to be closer to the true primary image without scattering rays. After initializing the primary image with the original X-ray image (step 220), scattering image estimation (steps 230 and 240) and A primary image in which scattering in the original X-ray image is corrected may be obtained through iteration of updating the primary image (step 250).

As described above, since an image is expressed as a sum image of a primary image and a scattering image, a difference or ratio between an original X-ray image and a sum image of a primary image and a scattering image may be a factor in updating a primary image.

Accordingly, the primary image may be updated according to the difference between the original X-ray image and the sum image of the primary image and the scattering image based on the primary image in the previous iteration (or initialized). In mathematical terms, it can be expressed as:

은 현재(n번째) 반복에서 갱신되는 프라이머리 영상을,

은 이전((n-1)번째) 반복에서 얻어진 프라이머리 영상을,

은

로부터 추정된 산란 영상을 나타낸다.

은 원본 X선 영상과 합영상 간 차이의 반영 정도를 결정하는(혹은 갱신 속도를 조절하는) 파라미터로, 반복 횟수와 무관한 특정 값(예컨대 0.1)이 될 수도 있고, 반복 횟수에 따라 변화되는(예컨대 점차 작아지는) 값이 될 수도 있다.here,

is the primary image updated in the current (nth) iteration,

is the primary image obtained in the previous ((n-1)th iteration),

silver

shows the scattering image estimated from

is a parameter that determines the degree of reflection of the difference between the original X-ray image and the sum image (or adjusts the update rate), and may be a specific value (for example, 0.1) independent of the number of repetitions, or changes according to the number of repetitions ( For example, it may be a value that gradually decreases).

The primary image may be updated according to the ratio between the original X-ray image and the sum image of the primary image and the scattering image based on the primary image in the previous iteration (or initialized). In mathematical terms, it can be expressed as:

When the primary video is updated in step 250, in step 260, the image processing unit 120 determines whether an end condition is satisfied, that is, whether to end repetition. If the end condition is not satisfied, the image processing unit 120 repeatedly performs steps 230 to 260 with the primary image updated through step 250.

와 이전 프라이머리 영상

의 차이가 소정 임계값 이하이면 종료 조건을 만족하는 것으로 볼 수 있다. 원본 X선 영상과 합영상 간의 비율(수학식 8)에 따라 프라이머리 영상을 갱신하는 경우, 예컨대 갱신된 프라이머리 영상

와 이전 프라이머리 영상

의 비율이 소정 임계값 이하이면 종료 조건을 만족하는 것으로 볼 수 있다. 실시예에 따라서는, 원본 X선 영상과 합영상 간의 차이 또는 비율과 무관하게, 종료 조건은 반복 횟수에 따라 판단될 수도 있다. 본 발명의 실시예에 따르면, 10회 정도의 반복이면

이 유의미한 값으로 수렴함을 확인할 수 있었다. 따라서, 예컨대 230단계 내지 250단계의 10회 반복을 종료 조건으로 정할 수도 있다.The end condition may be determined according to a difference or ratio between the updated primary video and the previous primary video. When updating the primary image according to the difference between the original X-ray image and the sum image (Equation 7), for example, the updated primary image

and previous primary video

If the difference between is less than a predetermined threshold value, it can be regarded as satisfying the termination condition. When updating the primary image according to the ratio between the original X-ray image and the sum image (Equation 8), for example, the updated primary image

and previous primary video

If the ratio of is less than a predetermined threshold value, it can be regarded as satisfying the termination condition. Depending on embodiments, the end condition may be determined according to the number of iterations, regardless of the difference or ratio between the original X-ray image and the summed image. According to an embodiment of the present invention, if it is repeated about 10 times

It was confirmed that convergence to this significant value. Therefore, for example, 10 repetitions of steps 230 to 250 may be set as an end condition.

은 n 번째 갱신된 프라이머리 영상이 된다.If the end condition is satisfied in step 260, the image processor 120 outputs the primary image updated in step 250 as a scattering corrected image in step 270. If n is the number of iterations when the termination condition is satisfied, the output image is expressed in the following equation.

Becomes the n-th updated primary picture.

7 shows an example of a scattering corrected image obtained according to an embodiment of the present invention. Referring to FIG. 7 , it can be confirmed that a scattering-corrected image (right) is obtained from an original X-ray image (left) including scattering components.

Meanwhile, if the WET map is incorrectly calculated in step 230, an error may occur in subsequent processes of estimating the scattered image (step 240) and updating the primary image (step 250). In particular, when the scattering component is excessively estimated, pixel values of the primary image become negative in the process of updating the primary image, and the primary image may not be properly improved even through repetition. Hereinafter, modified embodiments are presented in which additional processing is performed on the WET map to prevent miscalculation of the WET map.

로 칭하기로 한다.For convenience, the WET map obtained from the primary image through Equation 2 above is the first WET map as shown in the following equation.

shall be referred to as

In the original X-ray image, the direct exposure area is an area where X-rays do not pass through the subject and scattering does not occur, and pixels in the corresponding area must have a value of 0 in the WET map. However, for various reasons such as noise, the value of the WET map in the corresponding region may be greater than 0. Then, a scattering kernel that is not a zero function is applied to the corresponding area. In general, the pixel value of such a directly irradiated area is relatively high, so the estimated scattering component becomes large. In order to solve this problem, a part with a pixel value greater than a predetermined threshold is regarded as a direct irradiation region, and each pixel has a value of 0 or 1 according to the comparison between the pixel value of the original X-ray image and the threshold, so-called region of interest. (Region of Interest) masks can be created. That is, in the ROI mask, a pixel having a corresponding pixel value greater than the threshold may have a value of 0, and a pixel having a corresponding pixel value of the original X-ray image equal to or less than the threshold may have a value of 1. The threshold value is a value that serves as a criterion for distinguishing whether it is a directly irradiated area, and can be selected empirically in consideration of the sensitivity of the detector. can be selected as

8 is an example of a region-of-interest mask, the left side shows a given image, and the right side shows a region-of-interest mask. Referring to FIG. 8 , a portion of a given image having a pixel value greater than the threshold value is set to 0 (represented in black) in the ROI mask, and a portion of the given image having a pixel value less than the threshold value is set to 1 (represented in ROI mask). displayed in white).

라 하면, 다음 수학식에 따라 관심영역 마스크

를 이용하여 제1 WET 맵

을 제2 WET 맵

으로 변환할 수 있다.These region-of-interest masks

, the region of interest mask according to the following equation

The first WET map using

The second WET map

can be converted to

는 성분곱(elementwise multiplication)을 나타낸다.Here, operation

represents elementwise multiplication.

에서, 원본 X선 영상의 대응 픽셀값이 임계값보다 큰 픽셀(직접 조사 영역에 해당)은 그 값이 0으로 설정된다. 이렇게 구해진 제2 WET 맵

가 240단계에서 프라이머리 영상으로부터 산란 영상을 추정하는데 사용될 수 있다. 제2 WET 맵

는 직접 조사 영역에서 산란 커널이 영함수에 매핑되도록 할 수 있다.Therefore, the second WET map

, pixels whose corresponding pixel values of the original X-ray image are greater than the threshold value (corresponding to the direct irradiation area) are set to 0. The second WET map obtained in this way

In step 240, may be used to estimate a scattering image from the primary image. Second WET map

can cause the scattering kernel to be mapped to the zero function in the direct irradiation domain.

In addition, there are cases in which an X-ray irradiation area, that is, a field of view (FOV) is limited by using a collimator during X-ray imaging. In this case, the outer region of the collimator (for example, the black portion of the upper right edge in the left image of FIG. 8) is calculated as a 'thick' region when generating the WET map. If the scattering component is excessively estimated in the outer region of the collimator due to such an erroneous thickness calculation, image quality within the field of view may be adversely affected. To solve this problem, a so-called field of view (FOV) map having a probability value corresponding to each pixel corresponding to the field of view (FOV) may be generated from the original X-ray image. The field of view map may have a value of 0 to 1 as a probability value.

9 is an example of a field of view map, the left side shows a given image, and the right side shows a field of view map. FIG. 10 is an enlarged view of a part (red square) of FIG. 9 . Referring to FIGS. 9 and 10 , a portion having a high probability of corresponding to the visual field in the field of view map has a value of 1 or close to 1, and a portion of the field of view having a low probability of corresponding to the field of view has a value of 0 or close to 0. As shown in FIG. 10 , the field of view map has a probability value between 0 and 1.

As an example of a method of generating a field of view map, a field of view map may be derived by creating a learning model by learning subject images having a defined field of view using a machine learning (or deep learning) technique, and applying the given image to the learning model. As another example of a method of generating a field of view map, in a given image, an area with a very low pixel value (e.g., an area with a pixel value less than 25 in the case of a 12-bit image) is generated in the form of a mask with a value of 0 and the rest of the area with a value of 1. You may.

라 하면, 다음 수학식에 따라 제2 WET 맵

을 WET 맵

로 변환할 수 있다.these visual maps

, the second WET map according to the following equation

the WET map

can be converted to

가 240단계에서 프라이머리 영상으로부터 산란 영상을 추정하는데 사용될 수 있다. 이러한 WET 맵

는 직접 조사 영역 및 콜리메이터 바깥 영역에서 산란 커널이 영함수에 매핑되도록 할 수 있다.The WET map obtained in this way

In step 240, may be used to estimate a scattering image from the primary image. These WET maps

can cause the scattering kernel to be mapped to the zero function in the direct irradiation area and in the area outside the collimator.

11 shows an example of a WET map to which a region of interest mask and a field of view map are applied. Referring to FIG. 11 , it can be seen that the region of the WET map (right) corresponding to the non-region of interest (direct irradiation region) and the region outside the collimator in a given image (left) has a value of 0 and is displayed in black.

11 shows a WET map to which both the ROI mask and the field of view map are applied, but the WET map to which only the ROI mask is applied or the WET map to which only the field of view map is applied may be used according to embodiments.

Devices according to embodiments of the present invention include a processor, a memory for storing and executing program data, a permanent storage unit such as a disk drive, a communication port for communicating with an external device, a touch panel, a key, and a button. It may include user interface devices such as the like. Methods implemented as software modules or algorithms may be stored on a computer-readable recording medium as computer-readable codes or program instructions executable on the processor. Here, the computer-readable recording medium includes magnetic storage media (e.g., read-only memory (ROM), random-access memory (RAM), floppy disk, hard disk, etc.) and optical reading media (e.g., CD-ROM) ), and DVD (Digital Versatile Disc). A computer-readable recording medium may be distributed among computer systems connected through a network, and computer-readable codes may be stored and executed in a distributed manner. The medium may be readable by a computer, stored in a memory, and executed by a processor.

Embodiments of the invention may be presented as functional block structures and various processing steps. These functional blocks may be implemented with any number of hardware or/and software components that perform specific functions. For example, an embodiment may include an integrated circuit configuration, such as memory, processing, logic, look-up tables, etc., capable of executing various functions by means of the control of one or more microprocessors or other control devices. can employ them. Similar to components of the present invention that may be implemented as software programming or software elements, embodiments may include various algorithms implemented as data structures, processes, routines, or combinations of other programming constructs, such as C, C++ , Java (Java), can be implemented in a programming or scripting language such as assembler (assembler). Functional aspects may be implemented in an algorithm running on one or more processors. In addition, the embodiment may employ conventional techniques for electronic environment setting, signal processing, and/or data processing. Terms such as “mechanism”, “element”, “means” and “composition” may be used broadly and are not limited to mechanical and physical components. The term may include a meaning of a series of software routines in association with a processor or the like.

Specific executions described in the embodiments are examples, and do not limit the scope of the embodiments in any way. For brevity of the specification, description of conventional electronic components, control systems, software, and other functional aspects of the systems may be omitted. In addition, the connection of lines or connecting members between the components shown in the drawings are examples of functional connections and / or physical or circuit connections, which can be replaced in actual devices or additional various functional connections, physical connection, or circuit connections. In addition, if there is no specific reference such as “essential” or “important”, it may not be a component necessarily required for the application of the present invention.

So far, the present invention has been looked at with respect to its preferred embodiments. Those skilled in the art to which the present invention pertains will be able to understand that the present invention can be implemented in a modified form without departing from the essential characteristics of the present invention. Therefore, the disclosed embodiments should be considered from an illustrative rather than a limiting point of view. The scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the equivalent scope will be construed as being included in the present invention.

Claims (18)

(a) receiving an original X-ray image;
(b) initializing a primary image with the original X-ray image;
(c) estimating a scattering image from the primary image;
(d) updating the primary image using the original X-ray image and the scattering image;
(e) determining whether an end condition is satisfied;
(f) if the termination condition is not satisfied, repeating steps (c) to (e) using the primary image updated through step (d) as the primary image for step (c); and
(g) outputting the primary image updated through step (d) as a scattering-corrected image when the termination condition is satisfied;
In step (c),
generating a water equivalent thickness (WET) map from a flat field image and the primary image; and
and estimating the scattering image using the WET map and the scattering kernel. According to claim 1,
In step (d),
Scattering correction method for an X-ray image, characterized in that, based on the primary image, the primary image is updated according to a difference or ratio between the original X-ray image and the sum image of the primary image and the scattering image. . According to claim 1,
The scattering correction method of an X-ray image, characterized in that the scattering kernel is defined for each thickness. delete According to claim 1,
The step of generating the WET map,
A first WET map is generated from the flat field image and the primary image, and a region of interest having a pixel value of 0 in the first WET map, corresponding to a directly irradiated region of the original X-ray image. ) Scattering correction method of an X-ray image, characterized in that for converting to the WET map using a mask. According to claim 5,
The scattering correction method of the X-ray image, characterized in that the directly irradiated area of the original X-ray image is an area in which a pixel value is greater than a predetermined threshold value. According to claim 1,
The step of generating the WET map,
A first WET map is generated from the flat field image and the primary image, and a probability value corresponding to the field of view according to the collimator in the first WET map is a pixel value in the original X-ray image. A scattering correction method for an X-ray image, characterized in that for converting the field of view map into the WET map. According to claim 1,
In the step (e), the end condition is determined according to a difference or ratio between the primary image updated through the step (d) and the primary image in the step (c). Scatter correction method. According to claim 1,
In the step (e), the end condition is determined according to the number of repetitions of the steps (c) to (e). an image input unit that receives an original X-ray image; and
An image processing unit outputting a scattering-corrected image for the original X-ray image;
The image processor performs a first process of initializing a primary image with the original X-ray image and estimating a scattering image from the primary image, and updating the primary image using the original X-ray image and the scattering image. and a third process of determining whether an end condition is satisfied, and if the end condition is not satisfied, the primary video updated through the second process is used as the primary video for the first process. The first to third processes are repeatedly performed, and if the end condition is satisfied, the primary image updated through the second process is output as a scattering-corrected image;
The image processing unit generates a water equivalent thickness (WET) map from the flat field image and the primary image in the first process, and estimates the scattering image using the WET map and the scattering kernel. Scatter correction device for X-ray images. According to claim 10,
The image processing unit in the second process,
Based on the primary image, the primary image is updated according to a difference or ratio between the original X-ray image and the sum image of the primary image and the scattering image. . According to claim 10,
The scattering correction device for an X-ray image, characterized in that the scattering kernel is defined for each thickness. delete According to claim 10,
The image processing unit in the first process,
A first WET map is generated from the flat field image and the primary image, and a region of interest having a pixel value of 0 in the first WET map, corresponding to a directly irradiated region of the original X-ray image. ) X-ray image scattering correction device, characterized in that for converting to the WET map using a mask. According to claim 14,
The scattering correction device for an X-ray image, characterized in that the directly irradiated area of the original X-ray image is an area in which a pixel value is greater than a predetermined threshold value. According to claim 10,
The image processing unit in the first process,
A first WET map is generated from the flat field image and the primary image, and a probability value corresponding to the field of view according to the collimator in the first WET map is a pixel value in the original X-ray image. The X-ray image scattering correction device, characterized in that for converting the field of view map into the WET map. According to claim 10,
The end condition is determined according to a difference or ratio between the primary image updated through the second process and the primary image in the first process. According to claim 10,
The X-ray image scattering correction device, characterized in that the end condition is determined according to the number of repetitions of the first to third processes.

Images